This invention relates to a method and apparatus for securely authorizing performance of printing in a distributed postage meter system, and more particularly to a method and apparatus for ensuring debiting in a postage meter prior to its printing a postal indicia.
Traditional postage meters imprint an indicia on a mailpiece as evidence that postage has been paid. These traditional postage meters create the indicia using a platen or a rotary drum which are moved into contact with the mailpiece to imprint the indicia thereon. While traditional postage meters have performed admirably over time, they are limited by the fact that if the indicia image significantly changes, a new platen or rotary drum will have to be produced and placed in each meter. Accordingly, newer postage meters now take advantage of modern digital printing technology to overcome the deficiencies of traditional meters. The advantage of digital printing technology is that since the digital printhead is software driven, all that is required to change an indicia image is new software. Thus, the flexibility in changing indicia images or adding customized ad slogans is significantly increased.
Modern digital printing technology includes thermal ink jet (bubble jet), piezoelectric ink jet, thermal printing techniques, and LED and Laser Xerographic printing which all operate to produce images by dot-matrix printing. In dot-matrix ink jet printing individual print elements in the printhead (such as resistors or piezoelectric elements) are either electronically stimulated or not stimulated to expel or not expel, respectively, drops of ink from a reservoir onto a substrate. Thus, by controlling the timing of the energizing of each of the individual print elements in conjunction with the relative movement between the printhead and the mailpiece, a dot-matrix pattern is produced in the visual form of the desired indicia.
While digital printing technology provides the advantages discussed above, it also permits the size and weight of the meter to be dramatically reduced since the digital printhead is very small in size. Moreover, from an electronics architecture viewpoint the entire meter is now a distributed system having its various functions divided between numerous subsystems such as a vault subsystem and a printer subsystem. Each of the subsystems can communicate with each other but can also have independent processing capabilities permitting parallel processing of information and increased efficiency in operation. However, the downside of the above described distributed system is that when data is transferred over physically unsecured data lines, it is susceptible to interception and analysis utilizing, for example, a logic analyzer. If such interception and analysis occurs, the data signals may be capable of being reproduced. In the case of a postage meter, a vault typically accounts for the postage transaction prior to initiating printing of an indicia by the printer. Thus, if the vault print command signal can be reproduced, it may be possible to generate an indicia without having the associated accounting therefor taking place which would result in reduced revenues for the postal authority.